. Bulletin of the British Museum (Natural History), Geology. the marginal muscle (sensu Jessen 1972). The anterior faces of the spine and of the succeeding hemitrich bases are pierced by small, presumably vascular, foramina. The six proximal radials increase in length posteriorly, with the exception of the fifth, which equals the third in length in 37094. Each radial forms a stout shaft widening slightly towards the extremities. The third and fourth radials are slightly bent in the central region while the same region in the sixth radial bears narrow lateral pr1-6' mm Fig. 15 Macrose
. Bulletin of the British Museum (Natural History), Geology. the marginal muscle (sensu Jessen 1972). The anterior faces of the spine and of the succeeding hemitrich bases are pierced by small, presumably vascular, foramina. The six proximal radials increase in length posteriorly, with the exception of the fifth, which equals the third in length in 37094. Each radial forms a stout shaft widening slightly towards the extremities. The third and fourth radials are slightly bent in the central region while the same region in the sixth radial bears narrow lateral pr1-6' mm Fig. 15 Macrosemius rostratus Kgns,s\z. Base of left pectoral fin in ventral view, as preserved in 37094. (xi) Pelvic fin. The basipterygium resembles that of Amia (Fig. 16). The wide, dorsoventrally- compressed anterior expansion tapers gradually backwards, expanding sharply to form the arti- cular surface. The radials are not exposed in the specimens. The pelvic fin consists of six rays. The base of the leading ray is preceded by four very small splints of bone, the larger two forming a pair. These splints are probably reduced basal fulcra. All the pelvic rays except the first are segmented and branched. The bases of the ventral hemitrichia are produced laterally to form processes for the insertion of the fin inclinator muscles; the length of these processes decreases posteriorly. (xii) Anal and dorsal fins. The anal fin is large and rounded, with the rays widely spaced and approximately parallel. There are seven rays, each articulating with a long slender radial (37094, Fig. 17). Each hemitrich forms a lateral process at its base for the insertion of the inclinator muscles, as is usual. The leading, unbranched ray is shorter than the unsegmented proximal region of the second ray. The leading ray is preceded by a long, unpaired, asymmetrical splint, and by a pair of shorter splints. The number of dorsal fin-rays varies between 32 and 39; the dorsal fin-ray counts of six speci- mens are as f
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